package org.simantics.r.scl;

import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;

import org.rosuda.REngine.Rserve.RConnection;
import org.rosuda.REngine.Rserve.RserveException;
import org.simantics.scl.runtime.function.Function;

public class RSessionManager {
    static ConcurrentHashMap<String, RSession> CONNECTIONS =
            new ConcurrentHashMap<String, RSession>(); 
    
    public static RSession getSession(String id) {
        // CONNECTIONS is ConcurrentHashMap so no synchronization is needed here
        return CONNECTIONS.get(id);
    }
    
    public static RSession createSession(RSessionConfiguration configuration) throws RserveException {
        synchronized(CONNECTIONS) {
            String id = UUID.randomUUID().toString();
            return createSession(configuration, id);
        }
    }
    
    public static Object withConfiguration(RSessionConfiguration configuration, @SuppressWarnings("rawtypes") Function f) throws RserveException {
        RSession session = createSession(configuration);
        try {
            return session.syncExec(f);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            session.close();
        }
    }
    
    public static RSession getOrCreateSession(RSessionConfiguration configuration, String id) throws RserveException {
        synchronized(CONNECTIONS) {
            RSession session = getSession(id);
            if(session == null)
                return createSession(configuration, id);
            else
                return session;
        }
    }
    
    private static RSession createSession(RSessionConfiguration configuration, String id) throws RserveException {
        synchronized(CONNECTIONS) {
            RConnection connection = new RConnection(configuration.host, configuration.port);
            if(configuration.username != null && !configuration.username.isEmpty())
                connection.login(configuration.username, configuration.password);
            RSession managedConnection = new RSession(connection, id);
            CONNECTIONS.put(id, managedConnection);
            return managedConnection;
        }
    }
}